This application claims priority of German Patent Application No. 101 26 205.1 filed May 30, 2001.
The invention pertains to a releasable plug coupling with a protective sleeve for connecting fluid lines. Such plug couplings are used, e.g., in motor vehicle construction, to connect fuel lines to each other or to a fuel tank or fuel injector.
The plug coupling consists of a coupling housing with a cylindrical receiving space and a separate retaining element with elastic retaining edges that project radially into the receiving space for gripping behind the retaining lip after the insertion of the plug-in part into the receiving space.
The retaining edges are attached to support bodies that project into corresponding recesses in the housing wall when the retaining element is installed. By means of elastic connecting pieces that form a V, the support bodies are connected at their ends to pressure plates that extend outwards through corresponding openings in the housing wall and that can be pressed from the outside for releasing the coupling. In addition, the coupling housing includes a protective sleeve that can be moved against a spring force over the pressure plates of the retaining element.
A similar plug coupling with a protective sleeve is known, e.g., from EP 0 660 022 B1. Therein, the protective sleeve is configured as a cap that is integrally connected by two helical, bent elastic connecting pieces to a support ring that locks in an annular groove on the rear end of the housing. The protective cap is pushed over the housing wall by the force of the elastic connecting pieces such that the pressure plates are covered. This method effectively prevents an unintentional release of the coupling. To release the coupling, the caps must be pushed back until the pressure plates are visible and can be pressed together from the outside by the thumb and index finger. In this way, the retaining edges are moved away from each other and the retaining lip of the plug-in part is released so that the plug-in part can be pulled out.
The ""022 plug coupling has proven to have disadvantages wherein the individual parts are pressed against each other during packing and the protective caps can be pressed together with the plastic springs over a long time causing the springs to lose their spring force even before use. Also, the user cannot determine whether the plug-in part is engaged in the coupling housing without additional tools. Therefore, he must also pull on the plug-in part in order to guarantee that the retaining lip is also locked at the retaining edges.
The task of the present invention is to structure the plug coupling described above to prevent the risk of spring fatigue resulting from unfavorable storage and also to guarantee that the plug-in part is engaged correctly in the retaining element by means of a visual indication. This task is solved by the configuration of the protective sleeve described above, as well as by its connection to the coupling housing and the flexibility provided by a spiral spring. The use of a spiral spring made out of metal guarantees a long service life without the appearance of fatigue.
Here, before the plug-in part is inserted, the protective sleeve is located in front of the coupling housing such that the pressure plates of the retaining element can be seen easily. By inserting the plug-in part, the protective sleeve is pushed against the spring force over the head of the coupling housing until the pressure plates are completely covered. This is also a visual indication for the correct connection.
In order to release the plug connection when necessary, sleeve-wall sections having the width of the pressure plates have cuts at the edge of the protective sleeve between two locking tabs and these wall sections overlap the pressure plates when the plug-in part is inserted and can be pressed elastically against the pressure plates. The insertion can be made easier by cross grooves in the outer wall of the sleeve-wall sections.
To permit the locking tabs to be inserted into the grooves easily over the front edge while the protective sleeve is pressed onto the coupling housing, additional wall strips are cut from the edge of the protective sleeve on both sides of the locking tabs which make the locking tabs bend easier when the protective sleeve is pressed onto the coupling housing.